In the operation of these appliances, inertial forces tend to cause continued rotation of their tools for a considerable period after deactivation of the motor. This could cause injury to a person unaware of that continuing rotation, the risk of such injury being especially great in the case of equipment whose rotation is virtually noiseless. Appliances of this type are therefore conventionally provided with safety couplings including drum or disk brakes designed to arrest the load as soon as the motor is de-energized; these prior-art devices, however, are often cumbersome and relatively expensive, e.g. on account of their use of powerful magnets, and in many instances work rather abruptly, thereby causing shocks which eventually may damage the implement.